Serial transmission is one of data transfer forms that is executed in a data transfer system that is configured by an output circuit that transmits a data signal, a transmission channel through which the data signal passes, and an input circuit that receives the data signal. In the recent advanced information society, a high-speed data transfer technique is essential because of an increase in information capacity, and data transfer high in speed and low in data error rate is required for serial transmission. In order to realize such a technique, there is required to remove noise from the data signal to be transferred as much as possible. This is because in the data transfer environment with much noise, when the data signal is determined, the amplitude in the voltage direction is small, and the margin on the time axis is also small, thereby increasing the data error rate.
JP-A-2008-227991 discloses a technique for solving such problem that, in the serial transmission, when identical data continues, uplift occurs in the waveform of an output amplitude, and the amount of uplift becomes larger than half of the amplitude so as not to normally receive the data. In the technique, there is provided an identical-data continuation detector circuit, and an output of the identical-data continuation detector circuit is inputted to a driver circuit having a capacitor. When identical data continues, the driver circuit narrows the output amplitude so as to prevent the waveform from being uplifted at a receiver side.